Can anyone recommend a good book

I Certainly can. CGI Programming with Perl, 2nd ed. is an excellent book. It has an entire chapter on security, as any good CGI book should, and is very well written and easy to understand. It also uses excellent examples, and covers CGI.pm, templates, email, and a whole bunch of other good stuff. I'll stop typing now so you don't think the author paid me to post this ;-).